CAVES

Caves are hollow spaces carved into hillsides or underground by the action of water and the wind. On coasts, pounding waves sometimes hollow out caves in the bases of cliffs.

HOW ARE CAVES FORMED?

Caves are most common in limestone rock. Rainwater, which contains a weak acid, dissolves the soft limestone and seeps into cracks, eventually carving out channels that widen into tunnels and caves.
Caves are also found in glaciers and in cooled volcanic lava.

Water dripping from the ceiling of limestone caves contains dissolved minerals, such as calcite. Over thousands of years, tiny deposits of calcite build up on cave roofs to form hanging spiky columns called stalactites, and on the ground below to form stalagmites.